Swing doors heretofore used widely require a large space for opening because the door is opened with its full width turned about the support post. Accordingly, doors are known which comprise two or three unit segments each having a width one-half or one-third the width of the door and turnably connected together. When opened, the door flexes to a V-shape at the junctions of the adjacent segments, so that it has the advantage of reducing the shape needed for opening. However, this type of door is cumbersome to install, since the upper and lower ends of the door must be fitted in guide grooves formed in the lintel and sill so as to render the door moveable along the guide path.
Thus, with the doors other than swing doors which are made openable within a reduced space, it has been necessary to form the lintel and/or sill with a guide groove or special fixing means. Such doors, therefore, are unfit for home use.